Thumbwheel actuated vascular intervention device delivery system

ABSTRACT

A vascular intervention device delivery system, such as for implanting a self expanding stent, includes a thumbwheel rotatably mounted in a handle. A catheter has a proximal end attached to the handle and a distal carrier segment for mounting a stent thereon. A retractable sheath is movable to a position retracted proximally to uncover the distal carrier segment. A pull with a curved cross section extends between the thumbwheel and the retractable sheath. An idler wheel with a perimeter notch is rotatably mounted in the handle proximal to the thumbwheel. A pin is movably in the handle between a first position received in the perimeter notch to block rotation of the idler wheel, and a second position outside of the perimeter notch to permit rotation of the idler wheel. The pull wraps around the idler wheel to return in a direction for being wound onto a spool of the thumbwheel.

TECHNICAL FIELD

The present disclosure relates generally to vascular intervention devicedelivery systems, and more particularly to features that supportthumbwheel actuation for deployment of a vascular intervention device.

BACKGROUND

Self expanding stents and similar vascular intervention devices areoften delivered and deployed using so called pin and pull systems.Typically, the stent is compressed between a retractable outer sheathand an inner catheter. To deploy the stent, the user has to pull theouter sheath to uncover the stent using one hand while resisting theforce with the other hand on the inner catheter to maintain the positionof the stent during deployment. In pin and pull systems, the user canhave difficulty maintaining the inner catheter at a fixed position whilesimultaneously moving the outer sheath. In very difficult stentdeployments, which require a large amount of force by the user, thissimultaneous push and pull may lead to inaccurate stent positioning,shortening or lengthening of the stent, or possibly even damage to thestent or target vessel. Another disadvantage of pin and pull systems isthat there can be a lack of control on the deployment because the forceto deploy the stent decreases as more of the stent is deployed. If theuser maintains the same high force during deployment, the stent may bedeployed too fast for the user to control. Another potential problemrelates to building up tension in the outer sheath prior to movementsthereof during the deployment process. If the user pauses during thedeployment and releases this built up tension, deployment errors canoccur when the user resumes tension to again move the outer sheath tothe deployment position fully uncovering the self explaining stent.Another occasional problem relates to early partial deployment of astent due to friction on the retractable sheath enroute to a deliverysite.

The present disclosure is directed toward one or more of the problemsset forth above.

SUMMARY OF THE DISCLOSURE

A vascular intervention device delivery system includes a thumbwheelmounted in a handle. The thumbwheel has a spool and a radially outwardthumb surface. A catheter has a proximal end attached to the handle, anda distal carrier segment for mounting a vascular invention devicethereon. A retractable sheath is movable from a first position coveringthe distal carrier segment to a second position retracted proximallyuncovering the distal carrier segment. A pull extends between thethumbwheel and the retractable sheath. The pull has a cross sectionalshape with a concave side that is opposite to a convex side. An idlerwheel is rotatably mounted in the handle at a location proximal to thethumbwheel. The pull wraps around the idler wheel to return in adirection for being wound onto the spool of the thumbwheel.

In another aspect, a vascular intervention device delivery systemincludes a thumbwheel rotatably mounted in a handle. The thumbwheelincludes a spool and a radially outward thumb surface. A catheter has aproximal end attached to the handle and a distal carrier segment formounting a vascular intervention device thereon. A retractable sheath ismovable from a first position covering the distal carrier segment to asecond position retracted proximally uncovering the distal carriersegment. A pull extends between the thumbwheel and the retractablesheath. An idler wheel is rotatably mounted in the handle at a locationproximal to the thumbwheel. The idler wheel defines a perimeter notch. Apin is movably mounted in the handle, and is movable between a firstposition at which the pin is received in the perimeter notch to blockrotation of the idler wheel, and a second position outside of theperimeter notch to permit rotation of the idler wheel. The pull wrapsaround the idler wheel to return in a direction for being wound onto thespool of the thumbwheel.

In still another aspect, a method of operating a vascular interventiondevice delivery system includes inhibiting movement of the retractablesheath toward the second position while a distal end of the vascularintervention device delivery system is being maneuvered to a deliverysite at least in part by contacting the pull with a pin mounted in thehandle. The pin is moved out of contact with the pull when the distalend arrives at the delivery site. The retractable sheath is moved fromthe first position to the second position responsive to rotation of thethumbwheel in a reverse direction.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective schematic view of a vascular intervention devicedelivery system according to the present disclosure;

FIG. 2 is an enlarged view of the distal segment of the delivery systemshown outlined with a dashed line in FIG. 1;

FIG. 3 is a view similar to FIG. 2 about half way through a deploymentof a self expanding stent;

FIG. 4 is a perspective view of an assembly plate for the handle shownin FIG. 1;

FIG. 5 is a partial sectioned view showing the ratchet according to thepresent disclosure;

FIG. 6 is a sectioned side view through the thumbwheel of FIGS. 1 and 5;

FIG. 7 is a sectioned side view of a handle portion of a vascularintervention device delivery system according to another aspect of thepresent disclosure;

FIG. 8 is a top view of the inner workings of the vascular interventiondevice delivery system of FIG. 7, minus the handle;

FIG. 9 is a side view of a ratchet pawl for the vascular interventiondevice delivery system of FIG. 7;

FIG. 10 is a sectioned view through a portion of the vascularintervention device delivery system as viewed along section lines 10-10of FIG. 8; and

FIG. 11 is a partial perspective view of a portion of the handle fromFIG. 7 that includes the idler wheel.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, a vascular intervention device delivery system10 is shown before and during delivery of a self expanding stent 45 at adelivery site 51 in the vessel 50 of a patient. Delivery system 10includes a handle 11 that may be gripped in one hand by a user during adelivery procedure. Handle 11 may be manufactured from a suitable moldedplastic, such as in two longitudinal halves that are joined in anysuitable manner to form the complete handle 11. A thumbwheel 15 isrotatably mounted in the handle 11 and has a radially outward thumbsurface 16 and a spool 17. A catheter 30 has a proximal end 31 attachedto handle 11, and a distal carrier segment 32 for mounting a vascularintervention device, such as a self expanding stent 45, thereon.Proximal end 31 may take the form a Luer lock fitting to receive a wireguide, or so that treatment fluids or the like may be injected throughcatheter 30 in a manner well known in the art. A retractable sheath 37is movable with respect to catheter 30 from a first position coveringthe distal carrier segment 32 to a second position indicated by thedashed line in FIG. 3 at which the retractable sheath 37 has beenrefracted proximally to uncover the distal carrier segment 32. FIG. 3shows the retractable sheath 37 about half way between the firstposition and the second position.

A pull 38 extends between the spool 17 of thumbwheel 15 and theretractable sheath 37. Pull 38, which preferably is less elastic thanthe retractable sheath 37, may be attached to retractable sheath 37 atan attachment 39 in any manner known in the art, such as by welding pull38 to a metallic reinforcement of retractable sheath 37. In mostversions of the vascular intervention device delivery system 10 of thepresent disclosure, pull 38 will be longer than retractable sheath 37.Nevertheless, retractable sheath 37 could be longer than pull 38 withoutdeparting from the present disclosure. Pull 38 may comprise a metallicwire or thin band of metal, which may have a curved cross sectionalshape.

A wire retention/stability sheath 42 surrounds a majority of the lengthof pull 38, and serves to keep pull 38 in close proximity to the outersurface of catheter 30 over much of the length of delivery system 10.Wire retention/stability sheath 42 may be unattached to catheter 30,pull 38 or retractable sheath 37, but may be attached to move with pull38 and/or retractable sheath 37. On the other hand, wireretention/stability sheath 42 may be attached to catheter 30 at one ormore locations so that pull 38 and retractable sheath 37 also move withrespect to wire retention/stability sheath 42 during the deliveryprocess. Wire retention/stability sheath 42 may terminate and beattached at its proximal end at a fixation point within handle 11.

When in its pre-deployment configuration, as shown in FIGS. 1 and 2, avascular intervention device, such as a self expanding stent 45, isdisposed between an outer surface of the distal carrier segment 32 ofcatheter 30, and an inner surface of the retractable sheath 37. During atypical procedure, the distal carrier segment 32 is positioned at adelivery site 51 within a vessel 50 of a patient. After achieving properpositioning, the user then grips handle 11 and begins to rotatethumbwheel 15 so that pull 38 is wound onto spool 17. As this occurs,pull 38 and retractable sheath 37 move proximally with respect tocatheter 30 to allow the self expanding stent 45 to expand away fromcarrier segment 32 and into contact with the inner wall of vessel 50 ina manner well known in the art. During this process, catheter 30, or anouter catheter (not shown) that terminates adjacent stent 45, may beplaced in compression while both pull 38 and retractable sheath 37 arein tension. According to the present disclosure, handle 11 andthumbwheel 15 include a structure that allows thumbwheel 15 to rotate towind pull 38 onto spool 17, but prevent rotation in an oppositedirection. This aspect of the disclosure allows the user to stop thedeployment procedure while retaining the stored elastic energy in pull38 and retractable sheath 37.

Referring now in addition to FIGS. 4-6, a ratchet 20 provides thestructure that prevents thumbwheel 15 from rotating in a forwarddirection. In particular, handle 11 may be formed to include, or haveattached to an inner surface, an assembly plate 12 that defines a hub 13that receives an axle 36 upon which thumbwheel 15 is rotatably mountedto rotate about axis 14 in a reverse direction permitted by ratchet 20.Thumbwheel 15 includes a radially inward ratchet surface 31 of ratchet20. A ratchet pawl 22 of ratchet 20 is mounted in the handle 11, and hasa catch 23 in contact with ratchet surface 21 of thumbwheel 15. Ratchet20 holds thumbwheel 15 against rotation in a forward direction, but theretractable sheath 37 moves responsive to rotation of the thumbwheel 15in a reverse direction.

In the illustrated embodiment, catch 23 takes the form of a deformedrectangular shaped band of spring steel 24 that is received in anS-shaped groove 19 defined by assembly plate 12 and oriented parallel toaxis 14. The ratchet surface 21 of thumbwheel 15 may define a pluralityof stops 25 in each of four 90° rotation angles. In the specificembodiment shown, ratchet surface 21 defines at least fifty stops 25 perrevolution of thumbwheel 15 in order to provide the user with precisetactile control over the delivery procedure. The deformed band of springsteel 24 may have a width that contacts the ratchet surface 21 acrossthe width 26. In addition, although not necessary, the deformed band ofspring steel 24 may have a length 27 that is greater than radius 18 ofthumbwheel 15. An imaginary line 40 that extends parallel from an end 28of catch 23 to the axis 14 may be configured to be orthogonal to pull 38where pull 38 contacts spool 37, as best shown in FIG. 5.

Referring now to FIGS. 7-11, a vascular intervention device deliverysystem 60 according to another aspect includes a ratchet 70 and a handle61 with a structure that differs from that shown in relation to FIGS.4-6. However, where similar numbers are used, those features correspondto similar features shown in FIGS. 1-3. Vascular intervention devicedelivery system 60 differs from the system 10 described earlier by,among other features, the shape and structure of the ratchet pawl 72 andby the inclusion of a lock 80. Like the earlier version, ratchet 70provides a structure that prevents thumbwheel 66 from rotating in aforward direction.

Handle 61 may be formed from a suitable plastic to include a key shapedhub 62 that is received in a matching key shaped opening 74 defined byratchet pawl 72. This configuration permits assembly of ratchet pawl 72to key shaped hub 62 in a plurality of different but equivalent angularorientations. Key shaped hub 72 may define a central opening thatreceives an axle 63 to define an axis 64 about which thumbwheel 65rotates. Thumbwheel 65 includes a radially outward thumb surface 66 anda radially inward ratchet surface 71. Thumbwheel 65 may also include aspool 67 upon which the pull 38 is wound when the device delivery system60 is operated. In this version, the wire retention/stability sheath 42terminates at a junction box 43 (not shown in FIG. 7 for the sake ofclarity) positioned within handle 61. As in the previous version, thepull 38 is positioned within the wire retention/stability sheath 42 andemerges from the junction box 43 to wrap around an idler wheel 44 andreturn in a reverse direction for being wound onto spool 67 as bestshown in FIGS. 7 and 8. Idler wheel 44 is rotatably mounted in handle 61and positioned proximal to thumbwheel 65. As in the previous embodiment,ratchet 70 prevents thumbwheel 65 from rotating in a forward direction,but the retractable sheath 37 (FIGS. 1-3) moves responsive to rotationof thumbwheel 65 in a reverse direction.

In this embodiment, catch 73 takes the form of spiral arms 79 that areattached to a central body 76 by living hinges 77. Unlike the ratchetpawl 22 shown in the embodiment in FIGS. 4-6, ratchet pawl 72 may mostconveniently be formed of a suitable plastic material. When thumbwheel65 is rotated in a reverse direction, each of the three catches 73 willclick and be received into respective stops 75 that define ratchetsurface 71. In this embodiment, ratchet catches 73 are equallydistributed 120° apart around the axis 64 defined by axle 63. Thus, thethree catches 73 will simultaneously contact the ratchet surface 71 atthree different locations located 120° apart about axis 64. Thoseskilled in the art will appreciate that a ratchet pawl 72 having two,four or more catches 73 would also fall within the intended scope ofthis disclosure.

As best shown in FIGS. 7 and 9, the ratchet pawl 72 includes curved arms78 that are distributed to provide a circular guide for the thumbwheelas the ratchet teeth rotate around the fixed ratchet. Thus, in someembodiments, the use of curved arms 78 could permit omission of axle 63as shown, since the thumbwheel would rotate about axis 64 with thecurved arms 78 contacting ratchet surface 71, even without the inclusionof axle 63. It is also worth noting that this embodiment differs fromthe earlier embodiment in that both the ratchet pawl 72 and the ratchetsurface 71 of thumbwheel 65 may be made out of plastic, as opposed to ametal ratchet pawl 22 acting on a plastic ratchet surface 21 as in theearlier embodiment. By making both the pawl and the ratchet surface fromthe same material, the potential creation of the debris caused by theinteraction of metal with plastic can be avoided.

In addition to ratchet 70, vascular intervention device delivery system60 includes a lock 80 that allows thumbwheel 65 to be disabled duringshipment and during positioning of the distal carrier segment 32 (FIGS.1-3) at a delivery site 51 within a patient. The lock 80 is movablebetween a locked position, as shown, and an unlocked position shown inFIG. 11, and by dashed lines in FIG. 7. The lock 80 includes a latch 81positioned in handle 61 and movable along a line 82 between the lockedposition at which the latch 81 engages and contacts the radially outwardthumb surface 66 of thumbwheel 65, and the unlocked position at whichthe latch 81 is out of contact with the radially outward thumb surface66. Lock 80 also includes a pusher 85 that is at least partiallypositioned outside of handle 61, but on an opposite side of handle 61from the exposed portion of thumbwheel 65. The pusher may include awedge 86 that engages a post 83 of latch 81. Post 83 may be orientedperpendicular to the line 82 of action of latch 81. Vascularintervention device delivery system may be enabled by depressing pusher85 along line 87 to move latch 81 out of contact with radially outwardthumb surface 66 of thumbwheel 65.

Referring in addition to FIGS. 10 and 11, pull 38 may have a curvedcross section with a concave side 47 that is opposite to a convex side48, both of which are flanked by rounded edges 49. The concave side 47and the convex side 48 are the long sides of the pull 38 cross section.In the illustrated embodiment, the idler wheel 44 and the spool 67 arearranged so that the convex side 48 is in contact with idler wheel 48,and the concave side 47 is in contact with spool 67. Nevertheless, thoseskilled in the art will appreciate that the opposite configuration wouldalso fall within the scope of the present disclosure. Pull 38 may bepositioned between stability sheath 42 and catheter 30. As best shown inFIG. 10, the convex side 48 of pull 38 is in contact with the innersurface of stability sheath 42. The convex side 47 may be in contactwith, or adjacent to, the outer surface of catheter 30. In order toreduce friction, and reduce the contact area between pull 38 andstability sheath 42 as well as catheter 30, the radius of convex side 48may be smaller than the radius of the inner surface of stability sheath42. Likewise, the radius of concave side 47 may be less than the outerradius of catheter 30. Pull 38 may be manufactured from a suitable bandof spring steel to have the curved cross sectional shape shown in FIG.10. Pull 38 may be made from stainless steel with a sufficiently largecross section that the pull does not stretch when in tension at expectedmagnitudes (10's of Newtons) during a delivery process. The curved crosssectional shape of pull 38 may provide columnar support to retractablesheath 37 while the distal carrier segment 32 is being maneuvered todelivery site 51.

Latch 81 not only moves between positions in contact and out of contactwith thumbwheel 65, movement of lock 80 may also enable rotation ofidler wheel 44. In particular, idler wheel 44 may define a perimeternotch 46. A pin 55 is mounted to move with latch 81 between a positionin which pin 55 is received in perimeter notch 46 to block rotation ofidler wheel 44, and a second position (FIG. 11) outside of perimeternotch 46 to permit rotation of idler wheel 44. Pin 55 may include aknurled surface 56 that is in contact with pull 38 when pin 55 is in thefirst position received in perimeter notch 46. The knurled surface 56 isout of contact with pull 38 in the second position as best shown in FIG.11. Although pin 55 is shown as attached to a moving with latch 81, pin55 could be mounted to move independently of latch 81 without departingfrom the intended scope of the present disclosure. When pin 55 is in thefirst position received in perimeter notch 46 and has its knurledsurface 56 in contact with pull 38 as shown in FIG. 7, this interactionnot only serves to prevent rotation of idler wheel 44, but also servesto provide columnar support for pull 38 to support against movement ofretractable sheath 37 when the device is being maneuvered to a deliverysite 51 within a patient. For instance, friction on retractable sheath37 in the proximal direction during the maneuvering procedure isinhibited by the columnar strength provided by pull 38 and its contactwith pin 55. Those skilled in the art might appreciate that the knurledsurface 56 may help, but it is mostly believed to be the pressuredapplied by pin 55 onto the pull 38 that provides the columnar supportwhen the two features are in contact. Other potential options in placeof knurled surface 56 include but are not limited to a rubber overmoldon pin 55 to create friction on pull 38, or pin 55 could have a splinedsurface or maybe even a rough/smooth finish without departing from thepresent disclosure.

INDUSTRIAL APPLICABILITY

The present disclosure is generally applicable to vascular interventiondevice delivery systems, and more particularly to a delivery system fordelivery of self expanding stents and other vascular interventiondevices with self expanding action. The present disclosure findsspecific applicability to delivery of relatively long vascularintervention devices that produce substantial friction on the innersurface of retractable sheath 37, and thus require higher forces onretractable sheath 37 and pull 38 in order to successfully deliver thevascular intervention device to an intended treatment site.

The vascular intervention device delivery system 10, 60 will typicallybe packaged in a conventional sterile packaging in a known manner forshipment. After a wire guide (not shown) has been positioned in apatient's body across a treatment location, the catheter 30 may be slidover the wire guide to position the distal carrier segment 32 and theattached self expanding stent 45 at the delivery site 51 within thevessel 50 of the patient. Thereafter, the wire guide may be withdrawn orleft in place. During this portion of the procedure, the thumbwheel 65of the vascular intervention device delivery system 60 may be disabledby maintaining the lock 80 in its locked position as shown in FIG. 7. Itis also important to note that when the vascular intervention devicedelivery system 60 is being maneuvered to a delivery site 51 (FIG. 3)the pin 55 is received in perimeter notch 46 of idler wheel 44 toprevent idler wheel 44 from rotating and to place the knurled surface 56of pin 55 in contact with pull 38 to inhibit movement of retractablesheath 37 toward the proximal direction to uncover stent 45.

After the distal carrier segment 32 has arrived at and is properlypositioned at delivery site 51, and it is now time to deploy the selfexpanding stent 45, the user may depress pusher 85 to disengage lock 80and move latch 81 out of contact with the radially outward thumb surface66 of thumbwheel 65. This movement of lock 80 also moves pin 55 out ofperimeter notch 46 and out of contact with pull 38 as best shown in FIG.11. This movement enables rotation of idler wheel 44. In addition, whenpin 55 is moved out of contact with pull 38, the columnar support ofpull 38 is relieved, and readies pull 38 to support tension asthumbwheel 65 is rotated to take up the pull 38 on spool 67.

A method of operating vascular intervention device delivery system 10,60 includes rotating the thumbwheel 15, 65 in a reverse direction towind pull 38 onto spool 17, 67 to build up tension in the retractablesheath 37 and pull 38 without moving the retractable sheath 37 relativeto the distal carrier segment 32 of catheter 30. The “reverse direction”is clockwise in the view of FIG. 1 and counterclockwise in the view ofFIG. 7. In both cases, the “reverse direction” means that the user'sthumb moves toward their palm to rotate the thumbwheel 15, 65. Next, aportion, which is less than all, of the distal carrier segment 32 isuncovered by continuing to rotate the thumbwheel 15, 65 in the reversedirection. At some point during the delivery procedure, the user maythen pause rotation of the thumbwheel 15, 65 in the reverse direction.For instance, the user may pause in order to confirm that the vascularintervention device, such as a self expanding stent 45, is beingdelivered to the desired location in the vessel 50 of the patient. Whilethe rotation of the thumbwheel 15, 65 is paused, tension in the pull 38and the retractable sheath 37 is maintained by holding the ratchet 20,70 and preventing rotation of the thumbwheel 15, 65 in the forwarddirection. Ratchet 20, 70 may be considered to be in a holdconfiguration when catches 23, 73 are received in one of the stops 25,75 of the ratchet surface 21, 71. A remaining portion of the distalcarrier segment 32 is then uncovered to facilitate complete deploymentof the self expanding stent 45 by resuming rotation of the thumbwheel15, 65 in the reverse direction until retractable sheath 37 arrives atits second position fully uncovering distal carrier segment 32.

An important aspect of the ratchet operated vascular intervention devicedelivery system 10, 60 of the present disclosure is to allow forrotation of thumbwheel 15, 65 in one direction only. This means that thepull 38 and hence the retractable sheath 37 can only be pulledproximally. If the thumbwheel 15, 65 were able to rotate in bothdirections, it could cause the pull 38 to slack and possibly jump out ofthe collection diameter of the spool 17, 67 on thumbwheel 15, 65. Also,by keeping the rotation of thumbwheel 15, 65 to one direction only,ratchet 20, 70 allows all of the energy already placed in the system 10,60 by the user to be maintained. For example, if the user was topartially deploy a self expanding stent 45 that had a deployment forceof 30N the user will have to put effort into getting the stent topartially deploy. This effort could have caused the sheath 37 to stretchslightly and also the inner catheter 30 to compress slightly. If thisenergy were lost when the thumbwheel 15, 65 were released, it would meanthat when the deployment was resumed from that point, the user wouldhave to rotate the thumbwheel 15, 65 an amount in order to reestablishtension in the system 10, 60 again before the self expanding stent 45would continue to deploy. This may be especially important in the caseof deploying longer stents that require higher forces.

It should be understood that the above description is intended forillustrative purposes only, and is not intended to limit the scope ofthe present disclosure in any way. Thus, those skilled in the art willappreciate that other aspects of the disclosure can be obtained from astudy of the drawings, the disclosure and the appended claims.

What is claimed is:
 1. A vascular intervention device delivery system comprising: a handle; a thumbwheel rotatably mounted in the handle and having a spool and a radially outward thumb surface; a catheter with a proximal end attached to the handle, and a distal carrier segment for mounting a vascular intervention device thereon; a retractable sheath movable from a first position covering the distal carrier segment to a second position retracted proximally uncovering the distal carrier segment; and a pull extending between the thumbwheel and the retractable sheath, and the pull having a cross sectional shape with a concave side that is opposite to a convex side; an idler wheel rotatably mounted in the handle at a location proximal to the thumbwheel; and wherein the pull wraps around the idler wheel to return in a direction for being wound onto the spool of the thumbwheel.
 2. The vascular intervention device delivery system of claim 1 wherein one of the convex side and the concave side of the pull is in contact with the idler wheel; and an other of the convex side and the concave side of the pull is in contact with the spool.
 3. The vascular intervention device delivery system of claim 2 wherein the idler wheel defines a perimeter notch; a pin movably mounted in the handle, and being movable between a first position and a second position; wherein the pin is received in the perimeter notch to block rotation of the idler wheel in the first position, but being outside the perimeter notch to permit rotation of the idler wheel at the second position.
 4. The vascular intervention device delivery system of claim 3 wherein the pin has a knurled surface in contact with the pull in the first position; and the knurled surface is out of contact with the pull in the second position.
 5. The vascular intervention device delivery system of claim 4 including a lock slidably positioned in the handle, and being movable between a locked position in contact with the thumbwheel and an unlocked position out of contact with the thumbwheel; the pin is attached to move with the lock.
 6. The vascular intervention device delivery system of claim 1 wherein the thumbwheel includes a radially inward ratchet surface of a ratchet; a ratchet pawl of the ratchet being mounted in the handle and having a catch in contact with the ratchet surface; and the ratchet locking the thumbwheel against rotation in a forward direction, and the retractable sheath moving responsive to rotation of the thumbwheel in a reverse direction.
 7. The vascular intervention device delivery system of claim 6 wherein the idler wheel defines a perimeter notch; a pin movably mounted in the handle, and being movable between a first position and a second position; wherein the pin is received in the perimeter notch to block rotation of the idler wheel in the first position, but being outside the perimeter notch to permit rotation of the idler wheel at the second position.
 8. The vascular intervention device delivery system of claim 7 including a lock slidably positioned in the handle, and being movable between a locked position in contact with the thumbwheel and an unlocked position out of contact with the thumbwheel; and the pin is attached to move with the lock; wherein the pin is in contact with the pull in the first position; and the pin is out of contact with the pull in the second position.
 9. A vascular intervention device delivery system comprising: a handle; a thumbwheel rotatably mounted in the handle and having a spool and a radially outward thumb surface; a catheter with a proximal end attached to the handle, and a distal carrier segment for mounting a vascular intervention device thereon; a retractable sheath movable from a first position covering the distal carrier segment to a second position retracted proximally uncovering the distal carrier segment; and a pull extending between the thumbwheel and the retractable sheath; an idler wheel rotatably mounted in the handle at a location proximal to the thumbwheel, and the idler wheel defines a perimeter notch; a pin movably mounted in the handle, and being movable between a first position at which the pin is received in the perimeter notch to block rotation of the idler wheel, and a second position outside the perimeter notch to permit rotation of the idler wheel; and wherein the pull wraps around the idler wheel to return in a direction for being wound onto the spool of the thumbwheel.
 10. The vascular intervention device delivery system of claim 9 including a lock slidably positioned in the handle, and being movable between a locked position in contact with the thumbwheel and an unlocked position out of contact with the thumbwheel; and the pin is attached to move with the lock.
 11. The vascular intervention device delivery system of claim 10 wherein the pin is in contact with the pull in the first position; and the pin is out of contact with the pull in the second position.
 12. The vascular intervention device delivery system of claim 11 including a stability sheath; the pull is positioned between the catheter and the stability sheath, and the pull has a cross sectional shape with a convex side in contact with the stability sheath and a concave side.
 13. The vascular intervention device delivery system of claim 12 wherein the pull is a metallic band with a curved cross section.
 14. The vascular intervention device delivery system of claim 9 wherein the thumbwheel includes a radially inward ratchet surface of a ratchet; a ratchet pawl of the ratchet being mounted in the handle and having a catch in contact with the ratchet surface; and the ratchet locking the thumbwheel against rotation in a forward direction, and the retractable sheath moving responsive to rotation of the thumbwheel in a reverse direction.
 15. The vascular intervention device delivery system of claim 14 including a stability sheath; the pull is positioned between the catheter and the stability sheath, and the pull has a cross sectional shape with a convex side in contact with the stability sheath and a concave side; wherein the pull is a metallic band with a curved cross section.
 16. The vascular intervention device delivery system of claim 15 including a lock slidably positioned in the handle, and being movable between a locked position in contact with the thumbwheel and an unlocked position out of contact with the thumbwheel; the pin is attached to move with the lock; wherein the pin has a knurled surface in contact with the pull in the first position; and the knurled surface is out of contact with the pull in the second position.
 17. A method of operating a vascular intervention device delivery system that includes a thumbwheel rotatably mounted in the handle and having a radially outward thumb surface; a catheter with a proximal end attached to the handle, and a distal carrier segment for mounting a vascular intervention device thereon; a retractable sheath movable from a first position covering the distal carrier segment, and a second position retracted proximally uncovering the distal carrier segment; a pull extending between the thumbwheel and the retractable sheath; an idler wheel rotatably mounted in the handle at a location proximal to the thumbwheel, wherein the pull wraps around the idler wheel to return in a direction for being wound onto the spool of the thumbwheel, and the method comprising the steps of: inhibiting movement of the retractable sheath toward the second position while a distal carrier segment of the vascular intervention device delivery system is being maneuvered to a delivery site at least in part by contacting the pull with a pin mounted in the handle; moving the pin out of contact with the pull when the distal end arrives at the delivery site; moving the retractable sheath from the first position to the second position responsive to rotation of the thumbwheel in a reverse direction.
 18. The method of claim 17 including blocking rotation of the idler wheel during the inhibiting step at least in part by receiving the pin in a notch defined by the idler wheel; and wherein the step of moving the pin includes moving the pin out of the notch to enable rotation of the idler wheel.
 19. The method of claim 18 including contacting one of the convex side and the concave side of the pull with the idler wheel; and contacting an other of the convex side and the concave side of the pull with the spool.
 20. The method of claim 19 including rotating the thumbwheel in the reverse direction to build up tension in the pull without moving the retractable sheath relative to the distal carrier segment of the catheter; pausing rotation of the thumbwheel in the reverse direction; maintaining tension in the pull by locking a ratchet and preventing rotation of the thumbwheel in the forward direction. 